A few weeks ago, aboard a Southwest Airlines flight, I whipped out my Southwest Airlines Chase Visa to buy WiFi and a drink. I was a shameless brand junkie, copping a couple airline miles at the same time.

The next day, a woman purporting to be from JP Morgan Chase & Co.'s fraud department called my office. Had I authorized those transactions, she asked.

Seriously?

When I asked the rep why a Southwest Visa card had triggered a fraud alert on a Southwest Airlines flight, she noted that the transaction posted from Dallas.

Granted, my surfing session wasn't interrupted by a declined card. But it seemed a new frontier in financial chicanery when a bank suspects fraud on one of its branded partners' own properties.

Turns out, it's more of a reflection of how far banks have to go to combat it, experts say.

Overall, all types of identity fraud increased by more than 5 percent last year, affecting one in 20 consumers, according to Javelin Strategy & Research, with $21 billion stolen.

With credit card fraud, banks are on the hook. Federal law limits consumer liability on any fraudulent credit-card transaction to $50, though most credit card issuers won't hold you liable for anything because they want you as a customer. That liability leaves them aggressively trying to combat crooks.

"If the card is used fraudulently -- and it's happened to me, so I can speak from experience -- it's gratifying to know there are processes to freeze the card," said U.S. Bank spokeswoman Teri Charest.

Maybe so. But security industry insiders consider my experience a false positive. Perhaps you encountered one on your summer vacation. It can lead to a call like mine or, more inconveniently, an account block or card decline. Those don't work out well 3,000 or more miles or more from home.

Firms who provide anti-fraud security software for banks say false positives are a big problem. They threaten to drive customers to other banks. The reduce card-swipe fees.

But data on its frequency is hard to come by because banks try to keep it secret. Mike Buhrmann, CEO of Bellevue, Wash.-based Finsphere, a security software provider, claims on his blog that in some cases, banks can generate 40 false positives for each instance of actual fraud it catches.

It's led banks to keep statistics on how many customers they've turned off, said Ellen Joyner, principal of marketing manager for security intelligence at SAS in North Carolina.

"Customers definitely have a right to be annoyed because it means they aren't doing all they're doing to avoid this," she said.

In the past, anti-fraud software used rules to catch card fraud, she said. Software would trigger alerts if your card logged more than two transactions in five minutes, for instance, or if a magnetic stripe transaction follow an internet transaction, experts say. When a bank discovered a new fraud scheme, programmers wrote a rule, or computer code, to flag similar transactions or situations.

It was relatively cheap and easy to put in place. Trouble is, fraudsters change tactics as banks catch on.

SAS uses computerized customer profiles and behavior models in real time to try to detect fraud. SAS also tries to replicate your behavior on other bank cards, even though its customer might lack access to competitors' databases.

"We have a dynamic profile of you as your customer and how you behave and how you act," Joyner said. "There's a lot of additional information about how you currently are behaving and how you're behaving in the past."

But the new methods are getting adopted only slowly by an industry still smarting financially from the deep economic crisis of 2008-09.

"There are a lot of Top 10, Top 20 banks that are just now in the process of re-evaluating their technologies for these very reasons," Joyner said.

It's not hard to believe, based on the errors big banks continue to commit while servicing mortgage loans.

For now, you'll just have to live with occasional inconveniences. Here's what you can do to minimize them, beyond traveling with multiple cards: